Assessment of H2S Complaints

Transcription

1 Assessment of H2S Complaints Casey Middle School 3 High Street Boulder, Colorado Project Report March 25, 25 For: Boulder Valley School District 65 Arapahoe Rd Boulder, CO 833 (33) 447- By: Indoor Air Diagnostics Tulsa, Oklahoma Environmental Building Sciences, Inc. PO Box 364 Las Vegas, NM

2 March 25, 25 2 / OVERVIEW In response to reports of hydrogen sulfide (H2S) odors and health complaints in the Casey Middle School, Dr. Richard Shaughnessy of Indoor Air Diagnostics (IAD) and Mr. Brad Turk of Environmental Building Sciences, Inc. (EBSI) have conducted an assessment of the school. This work included a review of investigations and measurements conducted by others, consultation with BVSD staff and administration, site visits to assess pressure differences in the building and sewer pipes and to spot check H2S levels, and to provide recommendations for corrective action. These activities focused on indoor air quality problems related to, and assuming that, H2S was the source of the odors and complaints. FINDINGS H2S Spot Measurements During the site visit on February 27 and 28, 25, spot measurements of H2S were made in and around the building, and results are summarized in Table. A Jerome 63, with a lower detection limit of 3 ppb, was used to conduct all but one of the measurements. A Gray Wolf monitor was employed to sample the higher levels in the sewer pipe in the mechanical crawlspace. Two to four consecutive measurements of approximately 3 seconds in durations were made at each location. Measurements at all indoor locations were below the detection limit of the Jerome. The outdoor and garage measurements are at, or slightly above, the detection limit but the manufacturer of the instrument states that these results may be uncertain because of the cold temperature conditions. Building Pressure Measurements To confirm preliminary indications that the building was operating under a negative pressure with respect to outdoors, differential pressure measurements were made across the building enclosure at several locations, and under different operating conditions. Results are presented in Table 2. The results indicate that the HVAC systems do not overcome the natural depressurization of the building (due to stack effect, with HVAC systems off) on the first and second floors. The situation is aggravated slightly when exhaust fans (restroom fans, kitchen and lab exhaust hoods, etc.) are operated. Note that when classroom doors are open to the hallways, depressurization in the classrooms is often increased significantly implying that the supply and return/exhaust air flows in the hallways are unbalanced. The large, resulting depressurization can be a contributing factor in H2S migrating from minor leaks in sewer pipes. It can also cause undesirable air flow into the building, for example from the adjoining parking garage or from open windows that might be down-wind of sewer vent pipes on the roof. Sewer Vent Pipe Pressure Testing The District had previously installed air admittance valves (studor vents) and carbon scrubbers on the vent pipes on the roof. During the site visit in February, 25, some valves and scrubbers were found to have been impaired by frozen moisture that had collected in the devices.

3 March 25, 25 3 / To evaluate the impact on pressures in the vent pipes, pressure measurements were made at four cleanout locations in the building and at the top of the vent pipes, as valves and scrubbers were sequentially removed. As seen in Table 3, sewer pipes were found to be pressurized (with respect to indoors) at all test locations, including in the mechanical crawlspace, with all of the valves and scrubbers installed. With the pipes pressurized, H2S would be pushed from the pipes into the building (with any minute breach within the sewer pipes). This condition was gradually reversed (sewer pipes depressurized) as more valves and scrubbers were removed. With all of the devices removed, the vents operated as intended, driven by the stack effect and open top to produce negative pressures in the pipes at lower elevations and positive pressures near the tops of the highest vents, allowing the warm, buoyant, and H2S-laden air to release into the atmosphere. Note that because of the difference in roof elevations, with all vents open, the vent pipes on the lower roofs were slightly depressurized by the vent pipes on the taller roofs (C-wing). These pressures would likely change under different outdoor temperature and wind conditions. It appeared that, with vents open, the current locations of the vent pipes could allow re-entrainment of vented gases into outdoor air intakes for HVAC systems, and open windows and doors. RECOMMENDATIONS The following recommendations are primarily based on observations, tests, and findings during the site visits conducted in January 25 by IAD and in February by IAS and EBSI. The investigation focused on air quality problems related to migration of H2S into the building. ) Remove Carbon Scrubbers and Air Admittance Valves (studor vents) from roof-top plumbing vent pipes to relieve pressure build-up. Scrubbers and valves had problems with cold weather conditions, and appeared to permit pressure to build within the sewer lines running within the school boundaries. This, in combination with the building and underfloor space pressures running negative with respect to outdoors, could create unwanted entry of H2S from any minute breach, existing or future, in the sewer lines within the school boundaries. 2) Gang Together and Extend Plumbing Vent Pipes on the Roof. Keep discharge away from doors and operable windows and ventilation system outdoor air intakes. Overall design, decisions on location and length of extensions of vent pipes, and actual installation for optimal venting of sewer gases including H2S, should be overseen and engineered by professional Plumbing/Mechanical Engineering firm. 3) Keep Floor Drains and Other Traps Filled or Install Drain Check Valves. Mineral oil or other compatible fluid should be used in conjunction with water in the drains to slow drying out of traps. 4) Re-Balance HVAC System for the Entire Building and Underfloor Spaces (including mechanical spaces and crawlspaces), so as to achieve a very slight overpressurization with respect to outdoors. This will help assure that ) in combination with # and #2, above, H2S leakage from sewer pipes is minimized, 2) entry of outdoor air into the building is controlled to be through the HVAC equipment, and 3) entry of possible contaminants in the air from the open soil crawlspaces is reduced. Provide independent engineering oversight of test and balance process.

4 March 25, 25 4 / 5) Adjust or Modify ERV Wheel Wipers to reduce cross-contamination between fresh incoming air stream and stale air exhaust air stream (consult with manufacturer). 6) Assure that ERV Defrost Mode Rarely Occurs. To keep frost from accumulating and blocking air flow through the heat exchange wheel during very cold weather, ERVs will enter a defrost mode that stops cold incoming supply air, while maintaining exhaust flow thorough the wheel. This mode creates unbalanced air flows and depressurization of the building. The temperature setting for initiation of defrost mode should be carefully selected to avoid frozen wheels, yet minimize the period of time that exhaust air flows are greater than supply flows. 7) Increase Supply of Outdoor Air in order to ensure meeting ASHRAE recommendations. Earlier measurements of CO2 in classrooms suggest that the amount of outdoor air being provided to some areas of the building are below ASHRAE recommendations. The additional ventilation air is intended to flush and dilute indoor air pollutants to levels acceptable to the majority of occupants. 8) Consult with 3 rd Party Toxicologists and Health Professionals to ) evaluate possible causative agents for symptoms reported by staff and students, and 2) establish target indoor concentrations of potentially offending air pollutants. The target range established by health professionals is to be used as a basis to develop an air quality monitoring schedule within the school. In addition, a long-term maintenance program is to be put into effect to ensure the proper operation of the system and all modifications to be intact for the life of the occupied school building. 9) Implement a District-wide IEQ Program that includes a formal process for reporting IEQ complaints and responding to problems.

5 March 25, 25 5 / Table. Spot Measurements of Hydrogen Sulfide with HVAC Systems Operating, 2/28/5 Spot Measurement Location Displayed Concentration (ppb) () Outdoors, N-S Access Road East of School 3 to 5 (2) Parking Garage 4 (2) ERV OA Intake (Courtyard) 3 to 4 (2) ERV Exhaust (Courtyard) to 2 (2) Under Garage Slab Soil Air (3) : Loc T Loc T2 Loc T3 Crawlspace (3) : General Ground-source Heat Pumps Sewer Pipe at Cleanout 25 Crawlspace 2 (3) : General Crawlspace 3 (3) : General Crawlspace 4 (3) : General Electric Room at Floor Drain Non-Complaint Rooms (4) : Custodial Office B2 B35 Complaint Rooms (4) : C-wing st Flr Hall C2 C4 C-wing 2 nd Flr Hall C23 C24 C-wing 3 rd Flr Hall C33 C335 2 ()Jerome 63, with reported lower detection limit of 3 ppb, for all locations except sewer pipe in Crawlspace. (2)Outdoor air temperature at time of measurement approx. 24 F, wind ENE (5 th & High St.). Note that Arizona Instruments, manufacturer of Jerome 63, was not certain of the effect of cold outdoor temperatures at time of measurement on the sensor response and instrument accuracy. (3)See floor plan (Figure ) for approximate locations (4)Complaint and Non-complaint rooms as reported by BVSD Maintenance

6 March 25, 25 6 / Table 2. Building Pressure Difference Measurements (Pascals), 2/27/5 and 2/28/5 Location HVAC Off HVAC On HVAC On + All Exhaust On Exhaust Off Pressure / Door To Hall Pressure / Door To Hall st Floor West Door to Hall West Door by Grease Trap North Door to Hall East Door to Parking Garage C /Open -- C /Closed -4.3 /Open C /Closed -7.8 /Open C to -6. /Closed -- C /Closed -9. /Open C /Open -4.7 /Closed -.2 /Open C /Closed -6.8 /Open Door from Hall to Crawlspace nd Floor B25 Door to Courtyard C to +3. /Closed -3. /Open -- C /Open -- 3 rd Floor South Access Door to Roof to to +2.6 B /Open +.8 to +.2 /Open C /Closed +6.2 /Open -- C to +5. /Closed +3. to +5. /Open -- Note: All pressure measurements made with respect to outdoors, except for Crawlspace which is referenced to hall. Negative pressure difference values indicate space is depressurized, while positive values indicate pressurization.

7 March 25, 25 7 / Table 3. Sewer Vent Pipe Pressure Testing (Pascals), 2/28/5 Vent ID Opened (order of opening) (A) Cleanout in Crawlspace (Mech) (B) Cleanout in Mech. Rm. By Grease Trap Pressure Test Location (C) Cleanout in Hall by Garage (D) Cleanout in 3 rd Flr. Hall As Vents Opened (E) At Vent on Rooftop () All Vents Open All Open + Exh Fans On All Vents Capped (first) to to to to to A -.3 to to to (last) -3. to All Vents Open + All Exhaust Fans On to () Measurement at top of vent pipe, with top sealed to make pressure measurement (breezy conditions) Notes:. HVAC systems operating 2. Breezy conditions 3. All pressure measurements inside sewer pipe made with respect to inside of building (B-D), mechanical space in Crawlspace (A), or outdoors for vents on rooftop (E). See floor plan (Figure 2) for identification and approximate locations.

8 March 25, 25 8 / Figure. Plan showing location of crawlspaces and parking garage slab test holes.

9 March 25, 25 9 / Figure 2. Plan of sewer roof vent and pressure test locations and IDs.

10 March 25, 25 / WARRANTY Indoor Air Diagnostics (IAD) and Environmental Building Sciences, Inc. (EBSI) make no representation or warranty expressed or implied, with respect to its services, test results or findings, recommendations or results, and expressly disclaim the same. IAD and EBSI warrant that their services rendered are performed in accordance with procedures and practices generally understood in IAD s and EBSI s business to be careful and professional.